Show a folio without building its partners' folios (stage D5b)

Showing a folio built it and every folio holding a partner of its
symbols. Now a partner is built alone, as a symbol, into its folio's
scene (Diagram::buildSymbols()), and reused when that folio is built.

- A linked folio report built alone had no wires when it was linked,
  so its texts showing a wire's properties stayed empty: after any
  build, linked reports on the built folios and their partners look at
  their wires again, as opening does. Unlinked reports keep their texts,
  as opening leaves them.
- A report whose partner was built alone builds the partner's folio
  when its potential is followed.
- tableChainFolios() parsed every unbuilt folio's file. The index now
  lists the drawn tables and the table each continues (folio_table),
  and a .qetz opened from it uses that list. An index without it falls
  back to the folio files.
- A .qetz's project.sqlite is opened once per project
  (QetContainerDb::FolioReader), not once per folio built.

nuri (136 folios), opened fresh, one folio shown: median 1104 -> 184 ms,
each show builds one folio; industrial 234 -> 87 ms.

tst_lazyfolios: a folio whose table continues another is shown first
from a .qetz (fails when the index's chains are ignored). ctest 96/96
eager and lazy; 342-project corpus: master, lazy, .qetz lazy and .qetz
kept all the same.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/dataBase/projectdatabase.h

@@ -29,6 +29,8 @@
 #include <QSet>
 #include <QUuid>
 
+#include <optional>
+
 #include "../diagramcontext.h"
 #include "../titleblockproperties.h"
 #include "../conductorproperties.h"
@@ -164,12 +166,16 @@ class projectDataBase : public QObject
 		bool isBuildingFolio() const {return m_building_folios > 0;}
 		bool rowsFromDocument() const {return m_rows_from_document;}
 		QString schemaStamp() const;
-		QByteArray indexFile(const QList<std::pair<QUuid, QString>> &folio_headers);
+			/// A drawn table of a folio and the table it continues
+		struct FolioTable { QUuid table; QUuid folio; QUuid previous; };
+		QByteArray indexFile(const QList<std::pair<QUuid, QString>> &folio_headers,
+							 const QList<FolioTable> &tables = QList<FolioTable>());
 		void discardFill();
 			/// The tables are right as they are (filled from an index)
 		void markCurrent() {m_content_changed = false;}
 		bool fillFromIndex(const QByteArray &index, QList<std::pair<QUuid, QString>> *folio_headers,
-						   QString *why = nullptr);
+						   QString *why = nullptr,
+						   std::optional<QList<FolioTable>> *folio_tables = nullptr);
 		QString prefillReport() const;
 		QSet<QUuid> foliosWithUnjoinedWires() const;
 		QSet<QUuid> folioUuidsOfElements(const QSet<QUuid> &elements) const;